Introduction:
The Savage line of bolt action rifles not only lend themselves to easy barrel
swaps, but provide the opportunity for the careful hobbyist to modify the barrels
they have, or to install barrels that they have cut chambers for themselves.
These "wildcat" barrels are typically special purpose and can serve
to expand the flexibility of the Savage bolt action rifle. (Note that in order
to take advantage of wildcats you have to reload!) The most common wildcats
are "Improved" versions of existing cartridges, followed by standard
cartridges necked up or down to hold a different caliber bullet. An exampled
of an "Improved" wildcat was built on the authors rifle using only
a chamber reamers, gages and common tools.

Why wildcats?Wildcats are modified versions of existing "standard" cartridges.
Many (probably most?) of the existing "standard" cartridges started
out as wildcats. The 25-06, 270 Win, and 35 Whelen were all wildcats based on
the 30-06 case. The 223 and 222 magnum were based on the 222 Remington case.
The reason for wildcatting a cartridge is to fill some niche not filled by off
the shelf cartridges. Right now, wildcats for 6mm (.243) and 6.5mm (.260) are
all the rage for long range (600 and 1000yd.) shooting. Standard offerings (243,
6mm Rem, and .260 Rem) in these calibers are lacking in case capacities for
keeping heavy bullets supersonic at extreme range. (In order to take advantage
of the extra case capacities of these wildcats they use long barrels. The extra
powder goes towards keeping the pressure up as the bullet travels down the barrel
- not increasing peak pressure.) Wildcatting also provides cartridges in different
calibers based on the same case that will therefore feed in the same rifle.
There are several wildcats of the .223 case (6mm and 30 cal are the most common)
that were developed to provide larger caliber cartridges that feed properly
in AR style rifles.

Standard "Improved" Wildcats
Since I am assuming that the reader doesn't have access to a machine shop or
unlimited funds for manufacturing completely custom reamers, gages and reloading
dies this discussion is limited towards "common" wildcats for which
reamers and reloading dies are readily available. The most common of the wildcats
are the "improved" cartridges. These are cartridges that have the
same base and near the same length as their parent cartridge but are fatter
and have steeper necks so that they hold more powder. You will often see these
as "AI" cartridges such as 6mmAI. The AI stands for "Ackley Improved".
Ackley was a gun writer from way back that experimented and found that cases
with 40 degree necks and very fat body tapers could be reloaded more times than
the standard cases they were based on, even with hot loads.

The
AI wildcats also have the advantage that cases can be formed (carefully!) from
factory loaded ammunition or standard sized cases by fireforming. The downside
of course, is that the straight tapered cases don't feed properly from the magazine.
(This is especially true of push feed rifles like the Savage. ) Long range target
shooters generally don't care as they carefully single load each round anyway.
Another big advantage is that AI chambers can be formed by running the proper
reamer into an existing standard chambered barrel. This is exactly what will
be shown below to create a 22/250AI wildcat that equals the performance of the
220 Swift.